Experts warn risks ahead as US COVID-19 death toll surpasses 600,000

Experts are concerned that the Delta variant, which was first discovered in India, is on track to become a dominant strain of coronavirus in the United States.

The Delta variant, known by the scientific name B.1.617.2, has spread from where it was first discovered in India to over 60 countries, according to the World Health Organization.

This variant is highly transmissible, greater than the Alpha variant which is currently the dominant strain in the United States, Zhang told Xinhua. It may be associated with an increased disease severity, such as hospitalization risk, compared to Alpha, he added.

Scott Gottlieb, former commissioner of the US Food and Drug Administration, said the Delta variant could lead to new outbreaks in the fall, with unvaccinated Americans being the most at risk.

The CDC has elevated the Delta variant from "variant of interest" to "variants of concern".

Zhang urged more people to get vaccinated as soon as possible to keep the variant from taking hold. He also stressed the importance of keeping social distance, wearing masks and personal hygiene as vaccines could not offer 100 percent protection.